Incident Summary
While in the traffic pattern, the pilot lowered the landing gear. The pilot reported seeing the landing gear down green light illuminate and subsequently landed the airplane. However, during the landing, only the nose gear was in the down and locked position; the main landing gear were not down.
Examination Findings
Examination of the aircraft disclosed that the battery power was mostly depleted due to a broken alternator wire. The landing gear system was tested and it operated normally. The cause of the green light illumination despite only the nose gear being down remains unexplained by the system test.
System Details
According to the Cessna maintenance manual, the landing gear indicator light is connected in series. The manual states that the light will not illuminate unless all three landing gears are down and locked. This contradicts the observation that the light illuminated when only the nose gear was down. The alternator wire break may have contributed to abnormal electrical conditions, but the source does not establish a direct causal link.